1. Field
The presently disclosed subject matter relates to a LED lighting apparatus for lighting LEDs. More specifically, the subject matter relates to a LED lighting apparatus in which an amount of forward voltage for LEDs connected in series is larger than a supply voltage of a battery. The LED lighting apparatus can be used whenever a number of LEDs are used, such as in a vehicular lamp (e.g., tail-lights, stop lights, signal lights, headlights, etc.).
2. Description of the Related Art
FIG. 2 shows a conventional LED lighting apparatus 90 in which a plurality of LEDs 80 are connected in series and lit by use of a battery supply voltage that is lower than an amount of forward voltage of the LEDs 80. The conventional LED lighting apparatus 90 includes: a control circuit 91; a boosting circuit 92 controlled by the control circuit 91; an inverted boosting circuit 93 configured by using a charge pump circuit, and operated by the control circuit 91; wherein the LEDs 80 are connected between an output of the boosting circuit 92 and an output of the inverted boosting circuit 93 through a constant current circuit 96, if necessary. The conventional LED lighting apparatus 90 can light a requisite number of LEDs when a predetermined output voltage is supplied between the output of the boosting circuit 92 and the output of the inverted boosting circuit 93.
The control circuit 91 can control the predetermined output voltage by feeding back a voltage divided between resistors 94 and 95 so as not to raise the output voltage higher than the predetermined output voltage. The LEDs 80 can be connected in series to the constant current circuit 96 as shown in FIG. 2, and can be controlled to light with stable brightness characteristics as described in further detail, for example, in Japanese Patent Application Laid Open JP2005-136157 and its English translation, which are hereby incorporated in their entirety by reference.
In the conventional LED lighting apparatus 90 described above, because the inverted boosting circuit 93 is configured by using a charge pump circuit to allow the configuration to be simple, it is difficult to adapt the circuit to high power LEDs such as those used in vehicular lamps (e.g., signal lights, front lights, taillights, stop lights, etc.) When the conventional LED lighting apparatus is used for lighting high power LEDs in a vehicular lamp, for example, use of the constant current circuit 96 can result in some problems like runaway temperature increases (i.e., chip fever), large architecture of the chip, etc., which may result when the current in the device flows from several mil amperes to several amperes in a FET 96a and a resistor 96b located therein.
Thus, when high power LEDs that are used as a vehicular lamp such as stop lights are lit by the conventional configurative lighting apparatus, a plurality of middle-sized lighting apparatuses can be used for lighting the plurality of LEDs connected in either series or in parallel. In that case, because all of the LEDs are lit by the plurality of middle-sized lighting apparatuses, the conventional configurative lighting apparatuses can result in some problems such as complicated wiring and maintenance, increased cost, etc.
The disclosed subject matter has been devised to consider the above and other problems and characteristics. Thus, an embodiment of the disclosed subject matter can include a LED lighting apparatus for supplying LEDs connected in series with a requisite voltage and power even if the amount of forward voltage of LEDs connected in series is larger than a supply voltage of a battery. The various problems described above are thus addressed and possibly reduced or changed while also addressing and possibly reducing other associated problems.